The present invention relates to a polymer composition and its use for the manufacture of screw caps for bottles containing, in particular, drinks such as soda and carbonated or uncarbonated, mineral or natural, water.
The technical problem encountered in the use of plastic screw caps intended for bottles containing drinks is often related to the difficulty that the consumer has in unscrewing the cap from the bottle and to the unpleasant taste and unpleasant smell that the cap may give to the drink contained in the bottle. It is known to use a polyethylene composition containing an xe2x80x9camide waxxe2x80x9d which is, for example, the product of the reaction of a fatty acid with ammonia, an amine or a diamine. Screw caps manufactured with such a composition are easy to unscrew from the bottle but have the drawback of being able to transfer a taste and/or a smell to the contents of the bottle.
The WO Patent No 95/00599 describes a liner for reclosable container closure containing a lubricating agent such as silicones, fatty acid amines e.g. ethylene bis(stearamide), oleamide and erucamide, metal salts of fatty acids and inorganic materials such as talc, mica, fumed silica and calcium silicate.
The U.S. Pat. No. 4,256,234 describes a container closure having an easy openable liner. More particularly it describes the liner and the olefin resin composition of said liner that contains a conjugated diene polymer. The disclosed composition is used for a liner and not for a plastic screw caps as in the present invention.
The U.S. Pat. No. 5,834,079 describes a film having at least one layer containing a zeolite and an oxygen scavenger. The film layers disclosed in the Patent does not comprise all the components of the present invention composition.
The U.S. Pat. No. 3,923,198 describes a container that is hermetically sealed with an easy opening tape, at least a portion of which opacifies when stressed, providing a visual indication that the closure has been tampered with. The components of the present invention composition are used in different proportions.
A polymer composition used for screw caps for bottles containing drinks such as sodas and carbonated or uncarbonated, mineral or natural, water, which are easy to unscrew and at the same time avoid a taste and/or a smell being transferred to the drinks contained in the bottles, has been found.
The composition essentially comprises
(1) a polymer except a polymer based on a conjugated diene and
(2) at least one stabilizer chosen from neutralizing agents, short-term antioxidants, long-term antioxidants and UV stabilizers, and
(3) at least one additive in an amount from 0.01 to 1%, preferably from 0.1 to 0.4%, by weight chosen from
(a)natural, modified or refined lignite waxes or montan waxes,
(b)polyolefin-based or paraffin-based polar waxes, and
(c) refractory or metal oxides grafted by polar organic compounds, especially polyalkylene glycol compounds.